ErbB3 receptor tyrosine kinase (RTK) and its associated signaling regulate the development, maturation and function of the peripheral nervous system (PNS). Here we describe a new alternatively spliced ErbB3 variant (nuc-ErbB3) that is localized in the nucleus of Schwann cells (the glial cells of the PNS). Based on our preliminary data, nuc-ErbB3 controls proper axon recognition, axonal sorting and myelination by Schwann cells independent of the full-length ErbB3 receptor. nuc- ErbB3 possesses a functional nuclear localization signal sequence and binds to transcriptionally active chromatin. Using ChIP-ChIP arrays we identified the gene promoters that interact with nuc- ErbB3 and clustered the active promoters in Schwann cell gene expression. Our long-term objective is to elucidate the function of nuc-ErbB3 as a transcription factor and understand its role during the establishment of Schwann cell neuron interactions and myelination. Specifically, we aim to: 1. Determine the functional significance of nuc-ErbB3 in the establishment of axon-glial interactions and myelination, 2. Reveal the role of nuc-ErbB3 as a transcriptional regulator that influences the interaction of Schwann cells with axons and 3. Identify protein-binding partners of nuc-ErbB3 in the nucleus of Schwann cells and determine how they modulate nuc-ErbB3 function. We believe that the accomplishment of these aims will reveal a new concept for membrane receptor tyrosine kinase regulation of cellular processes in the nervous system through their alternatively spliced nuclear variants. Moreover, exploration of the transcriptional role of nuc-ErbB3 and its function during axon-glial interactions and myelination will provide useful information in relation to peripheral neuropathies caused by deregulated gene expression and/or altered myelin formation.